The present invention relates to an electronic components mounting/connecting package for mounting electronic components such as semiconductors and the like on circuit boards or film carriers and its fabrication method.
It has been known for many years to connect bump electrodes of a semiconductor to patterning electrodes of a circuit board by press-bonding with an insulating resin placed between the semiconductor and the circuit board and this has been referred to as a microbump bonding method. With the help of FIG. 12, this microbump bonding method will be explained here.
In FIG. 12(a), item 121 is a circuit board composed of glass, ceramics or the like, item 122 is a patterning electrode formed on the circuit board 121 and item 123 is a drop of a light setting insulation resin placed at a position on the circuit board where an LSI chip is to be mounted. Then, as illustrated in FIG. 12(b), a bump electrode 126 formed on an aluminum electrode 125 of the LSI chip 124 is aligned in position with the patterning electrode 122. The bump electrode 126 has been so far comprised of such a metallic material as gold, solder or the like and has been formed on the aluminum electrode 125 of the LSI chip 124 either directly by an electrolytic plating method or through a transferring method whereby metal bumps formed on a separate metal substrate are transferred to the surface of the aluminum electrode 125 of the LSI chip 124.
In the next, as illustrated in FIG. 12(c), the LSI chip 124 is applied with a pressing force through a pressure application tool 127. Then, the insulation resin 123 under the bump electrode 124 is completely put aside towards the periphery and the bump electrode 124 is compressed to complete an electrical connection with the patterning electrode 122. Then, ultraviolet rays 128 are irradiated for curing the light setting insulation resin 123, as shown in FIG. 12(d). At this time, when the circuit board is formed of a transparent material such as glass, etc., the ultraviolet rays are irradiated from the back side of the circuit board 121 and when the circuit board is not transparent, the ultraviolet ray irradiation is applied from the side where the LSI chip 124 is mounted. When curing of the resin is finished and the pressure application tool 127 is removed, the connection between the LSI chip 124 and the circuit board 121 will be finally completed, as shown in FIG. 12(e).
However, the aforementioned method of the prior art has a few problems as in the following:
1) As the number of connecting pins increases, their weight becomes so large as to make the semiconductor and the circuit board liable to deform, leading to deterioration in connection reliability and sometimes to causing a damage to the semiconductor itself. PA1 2) The pressure application to from tens to hundreds of electrodes formed on semiconductors has to be performed uniformly and a very high accuracy has to be realized in flatness on both of the pressure application tool and the opposing surface of the circuit board and the degree of the accuracy required will be increasing as the number of the connecting pins increases and the chip size becomes large, resulting in difficulties to meet the requirement. Even a small variation in height distribution of the bump electrodes, by 3 to 5 um for example, or a slight warp of the circuit board will be causing failures in connection. PA1 3) Also, when the semiconductors are turned on to operate, the heat generated from the semiconductors tends to bring about straining and warping to the materials used due to differences in thermal expansion coefficient, consequently leading again to failures in connection between the bump electrodes and the circuit board electrodes.
The connection failures as described in the foregoing take place not only with the microbump bonding method but also with the flip-chip bonding method that uses solder bumps.